[ARDF] TRO-2 ARDF transmitters...

[Kenneth E. Harker]

On Fri, Feb 24, 2006 at 11:58:14AM -0800, Marvin Johnston wrote:
> 
> Take a look at:
> 
> http://www.west.net/~jay/turnstile.html

Jen and I have built eight of these antennas and they work fine.

Our variation of this design is to use:

4 ea. 8-32 x 1" round-head machine screws (in place of 3/4" long)
4 ea. aluminum arrow shafts cut to length with Dremel tool (in place of 
  1/8" diameter uncoated bronze welding rod and 8-32 1" long hex spacers)

We figured the arrow shafts would look cool and would be easier to deal with
than figuring out how to (a) find the hex spacers and rods and (b) bond them 
together.  We discovered, however, that:

* Not all aluminum arrows use aluminum threading for the arrow heads - some
  have plastic inserts.

* The threading starts quite a ways inside from the end of the arrow - this 
  means that the machine screw sticking out of PVC needs to be longer.  With a 
  1.25" PVC cap, the longest screw you can possibly work through is 1", and
  that was just marginally long enough for the arrows to have enough threading
  to catch.  If I were doing it over, I'd use a 1.5" PVC cap and 1.25" long
  screws.

* Arrows will stand up well to abuse, should result in a more broadbanded
  antenna, and with the appropriate end cap should really not pose much
  risk to eye damage, but they're not as cheap as other element material.

All of our antennas have a SWR between 1.3:1 and 1.4:1 or so.  This 
doesn't seem to be a big deal in practice.
 
> These are the turnstile antennas we used for the 2004 Championships, and
> what I use for all the hunts that I put on and course set in So. Cal.
> They were built by Jay specifically for the 2004 ARDF Championships, and
> work very well!
> 
> BTW, I just found out that Jay's (WB6RDV) "warmup" for the practice at
> Topanga Canyon will be a 10K competition run that morning. Ohio, are you
> paying attention :).
> 
> More information about that hunt at http://www.homingin.com/.
> 
> Marvin, KE6HTS
> 
> 
> 
> Matthew Robbins wrote:
> > 
> > Here in Cincinnati, we've been building G3ZOI's TRO-2 transmitter.
> > I've put up some photos at http://offcycle.org/ .
> > 
> > We had some questions about sizing the phasing harness on a turnstile
> > antenna.  Perhaps someone here can make it a little more clear.
> > 
> > Matthew
> > AA9YH
> > Cincinnati, Ohio USA
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-- 
Kenneth E. Harker WM5R
kenharker at kenharker.com
http://www.kenharker.com/